Mercury in the San Francisco Estuary - Reviews of Environmental Contamination and Toxicology - page 44

hydraulic mining debris and had an impact on the distribution of mercury-contaminated
sediment (James 2005), but mercury itself was not specifically considered. In the
early 1970s, concentrations in striped bass and catfish in the estuary were found to
exceed the federal guidelines, and fish consumption advisories were issued by the
State Department of Health (NRC 1978). Between 1970 and 1990, economic pressure
and regulatory measures by the U.S. Environmental Protection Agency (EPA), such
as the cancellation of product registration for mercury-containing pesticides, led to
the rapid decline of its use in the region (Sznopek and Goonan 2000). These regula-
tory measures and a decline in economic viability resulted in the closure of most of
the region's mercury mines in the early to mid-1970s (Cargill et al. 1980). The New
Almaden mining district closed in 1975 and is listed on the EPA's Abandoned Mine
Lands CERCLIS (“Superfund”) inventory (USEPA 2007a).

B Recent Management and Restoration Efforts

The thread of recent management efforts in the estuary begins in 1994, when the State
of California's Bay Protection and Toxic Cleanup Program measured mercury con-
centrations in fish that humans consume from San Francisco Estuary (Fairey et al.
1997). Based on the results, a health advisory for consuming fish from the estuary
caused the San Francisco Bay Regional Water Quality Control Board (SFRWQCB)
to formally list San Francisco Bay as impaired by mercury (Davis et al. 2002). Since
1999, the SFRWQCB has been developing a Total Maximum Daily Load (TMDL) to
determine the load reductions necessary to attain the water quality standard for mer-
cury (Johnson and Looker 2003; SFRWQCB 2006). The development of the TMDL
is based on data from the Regional Monitoring Program (RMP) for Water Quality in
San Francisco Estuary that identified the magnitude of mercury contamination as well
as the temporal and spatial variability of concentrations in water, sediment, and biota
(Conaway et al. 2003, 2007; Hoenicke et al. 2003; Thompson et al. 2000). The results
of numerous other research projects from San Francisco Estuary, already described,
and other mercury-contaminated locations have provided the current basic under-
standing of the processes affecting mercury biogeochemistry in the estuary.
Published studies on the effects of mitigation or remediation on environmental
mercury are notably lacking for San Francisco Estuary. A laboratory study by
Mehrotra and Sedlak (2005) used iron additions to decrease mercury methylation
in wetland sediments from locations surrounding the estuary. In addition, phytore-
mediation of mercury-contaminated sediments using water hyacinth ( Eichhornia
crassipes ) has been evaluated in the delta region of the estuary (Greenfield et al.
2007; Riddle et al. 2002). Nonetheless, there is a dearth of published papers on
mercury experiments using constructed, managed, or remediated wetlands for the
estuary. Compounding this lack of information, the scale of design and implemen-
tation of wetland restoration activity in San Francisco Estuary is changing from
small restoration activities to large, landscape-scale projects, such as the 60 km 2
South Bay Salt Pond Restoration Project (Simenstad et al. 2006).